Hydraulic pump for excavator and excavator comprising the same

ABSTRACT

A hydraulic pump for an excavator, which comprises a housing having a supporting wall extending therein; a pair of rotary hydraulic cylinders provided in the housing, each of the rotary hydraulic cylinders being provided with a piston which is movable reciprocatingly in the rotary hydraulic cylinder; and a pair of spindles disposed parallel to the rotary hydraulic cylinders, the spindles being connected with each other via a coupler and driving the rotary hydraulic cylinders to rotate about their respective central axes, each of the rotary hydraulic cylinders comprising a swash plate for receiving and guiding the piston, and the swash plate being stationary relative to the respective spindle, wherein the supporting wall comprises a mounting hole, and the coupler is supported in the mounting hole by means of a sliding bearing.

TECHNICAL FIELD

The present invention relates to a hydraulic pump, in particular to ahydraulic pump for an excavator, and to an excavator comprising thehydraulic pump.

BACKGROUND ART

A hydraulic pump used in an excavator generally comprises a housing anda pair of rotary hydraulic cylinders accommodated in the housing. Therotary hydraulic cylinders are disposed coaxially opposite to eachother. A driving shaft is supported in the housing parallel tolongitudinal axes of the rotary hydraulic cylinders. Two swath platesare mounted in the housing fixedly relative to the driving shaft. In therotary hydraulic cylinder there is provided with a reciprocating piston.Each of the swash plates comprises a mating surface for receiving andguiding the piston. Each of the rotary hydraulic cylinders is driven torotate about a central axis of the driving shaft, and thus the piston isdriven to move reciprocatingly in the respective rotary hydrauliccylinder as the driving shaft rotates.

In the prior art, in order to reduce manufacturing and assembly cost,the driving shaft mentioned above is configured as two separate spindleswhich are disposed coaxially with each other and have substantially thesame length, the two spindles being connected with each other via acoupler. A needle bearing for supporting purpose is providedsubstantially in the middle of the driving shaft and therefore at thecoupler because the driving shaft formed by connecting via the coupleris long, which provides sufficient support to the driving shaft andprevents the driving shaft from bending and deforming caused by the longdriving shaft consisting of the coupler.

On one hand, the needle bearing has a relative precise structure, and onthe other hand, the excavator generally works under bad conditions. Thiscauses a loud noise to be generated during the running of the needlebearing in the hydraulic pump and causes a high failure possibility. Thehydraulic pump works at a low work efficiency and may even be damaged,and then the service life of the excavator is affected and itsmaintenance period is shortened.

It is thus desired to improve the bearing of the hydraulic pump in termof its service life and to reduce the failure possibility of thebearing, in order to improve the work efficiency of the hydraulic pumpand to prolong the service life of the excavator or the maintenanceperiod.

In addition, the swash plates may be disposed at an angle relative tothe driving shaft depending on the work conditions, and a certainbending moment or a centrifugal force can then be generated (the reasonswill be described in the following description) at the coupler when thedriving shaft is driven to rotate. Excessive bending moment orcentrifugal force may cause an excessive vibration on the driving shaft,and then the efficiency of the hydraulic pump will be affected.

It is thus desired to decrease the bending moment as possible as it canby improving the hydraulic pump, to reduce the vibration of the drivingshaft and thus improve the efficiency of the hydraulic pump.

SUMMARY OF THE INVENTION

An object of the invention is to provide a hydraulic pump and anexcavator comprising the hydraulic pump, which have prolonged servicelife and reduced manufacturing cost, to reduce vibration of a drivingshaft in the hydraulic pump and to improve efficient of the hydraulicpump.

According to one aspect of the invention, a hydraulic pump for anexcavator is provided, which comprises a housing having a supportingwall extending therein; a pair of rotary hydraulic cylinders provided inthe housing, each of the rotary hydraulic cylinders being provided witha piston which is movable reciprocatingly in the rotary hydrauliccylinder; and a pair of spindles disposed parallel to the rotaryhydraulic cylinders, the spindles being connected with each other via acoupler and driving the rotary hydraulic cylinders to rotate about theirrespective central axes, each of the rotary hydraulic cylinderscomprising a swash plate for receiving and guiding the piston, and theswash plate being stationary relative to the respective spindle, whereinthe supporting wall comprises a mounting hole, and the coupler issupported in the mounting hole by means of a sliding bearing. Accordingto the above technical solution of the invention, the sliding bearinghas a relative simple structure, a more impact resistant property, asignificantly prolonged service life, and a reduced manufacturing cost,and the noise generated during its running is low. Optionally, the swashplate has an adjustable angle relative to the spindle to adjust anamount of a stroke of the piston in the rotary hydraulic cylinder.

Preferably, the hydraulic pump is provided with an adapting bushingtherein, and the sliding bearing is mounted in the mounting hole via theadapting bushing so that the adapting bushing is located between anouter circumferential surface of the sliding bearing and an innersurface of the mounting hole. The adapting bushing is made of a materialdifferent from that of the sliding bearing. For example, the adaptingbushing is made of a steel material, in particular an alloy steelmaterial, while the sliding bearing is made of a powder metallurgymaterial. Accordingly, the sliding bearing is not directly mounted inthe mounting hole of the supporting wall, but via the adapting bushing,which results in the wear to the housing itself being reduced and theservice life of the hydraulic pump being prolonged.

Preferably, a circumferential flange extends out radially from an outercircumferential surface of the adapting bushing near an end of theadapting bushing which is adjacent to a surface of the supporting wall,and the circumferential flange is configured for contacting with thesupporting wall. The circumferential flange is configured for fixing theadapting bushing into position, preventing the adapting bushing frombeing displaced during mounting or after mounting and thus ensuring thenormal work of the sliding bearing.

Preferably, the sliding bearing is configured as a pair of slidingbearings axially spaced from each other; and/or the adapting bushing isconfigured as a pair of adapting bushings axially spaced from eachother. In this way, heat generated during the running of the hydraulicpump and in particular during the rotating of the coupler can bedissipated more rapidly, and the temperature of the sliding bearings isreduced. In addition, the manufacturing cost is reduced accordinglybecause the material from which the sliding bearings and/or the adaptingbushings are manufactured is expensive. This also results in a smallerbending moment generated at the bearing during the running of thehydraulic pump (details will be described in the following), and thusthe vibration generated on the spindle is reduced or even eliminated.The work efficiency of the hydraulic pump is therefore improved.

Preferably, the supporting wall is formed with an oil guiding hole, andthe oil guiding hole is aligned with and communicated with an axial gapbetween the adapting bushings. Lubricant oil can be injected into theaxial gap via the oil guiding hole to lubricate the bearing and cool thesliding bearing when the spindle rotates. It is conceivable that the oilguiding hole can be configured for receiving oil leaked in the runningof the rotary hydraulic cylinders, so that the leaked oil can pass bythe sliding bearing and flow out via the oil guiding hole after coolingthe bearings.

Preferably, the sliding bearing is provided with chamfers at oppositeends, so that the sliding bearing can be easily inserted into themounting hole or into the adapting bushing when assembling, andlubricant oil can reach the sliding bearing more easily to achieve agood lubricant effect.

Preferably, the adapting bushing is provided with chamfers at oppositeends and preferably out-chamfers, so that the adapting bushing can beinserted into the mounting hole easily.

Preferably, a pair of spherical splines are amounted between the couplerand the spindles. According to another aspect of the invention, anexcavator comprising the hydraulic pump described above is provided.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects of the invention will be better understoodfrom the following description in conjunction with the drawings, inwhich:

FIG. 1 shows an axial cross-sectional view of a hydraulic pump accordingto one illustrative embodiment of the invention;

FIG. 2 shows an enlarged view of a portion of the hydraulic pump shownin FIG. 1;

FIG. 3 shows an axial cross-sectional view of a hydraulic pump accordingto another illustrative embodiment of the invention;

FIG. 4 shows an enlarged view of a portion of the hydraulic pump shownin FIG. 3; and

FIG. 5 is similar to FIG. 4, showing an enlarged view of a portion of ahydraulic pump according to a further illustrative embodiment of theinvention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Illustrative embodiments of the invention will be described withreference to the drawings. It should be noted that same referencenumbers throughout the drawings denote functionally and/or structurallyidentical elements or devices.

FIG. 1 shows an axial cross-sectional view of a hydraulic pump 1according to one embodiment of the invention. The hydraulic pumpaccording to the invention can be used in a mechanical device working inbad conditions, for example in an excavator.

As shown in FIG. 1, the hydraulic pump 1 comprises a housing 2 and endcaps 3 and 4 mounted on opposite ends of the housing 2. Two spindles 5and 6, two rotary hydraulic cylinders 9 and 10, and two swash plates 7and 8 for driving the rotary hydraulic cylinders are provided in thehousing 2. The swash plates 7 and 8 are configured for adjusting workingstrokes of the rotary hydraulic cylinders 9 and 10 respectively.

The two spindles 5 and 6 are disposed coaxially and are connected witheach other at their opposite ends via a coupler 13 in a known way. Inthe illustrated embodiment, the spindle 5 comprises an end which extendsout of the end cap 3 to be connected with a driving device, for example,a diesel engine (not shown), so that the two spindles 5 and 6 can bedriven by the driving device to rotate.

For example, the swash plate 7 is mounted on the end cap 3 fixedlyrelative to the housing 2, and for example, the swash plate 8 is mountedon the end cap 4 fixedly relative to the housing 2. The swash plates 7and 8 comprise central openings respectively, and the central openingsare sized such that the spindles 5 and 6 can pass through the centralopenings respectively without contacting with them.

The rotary hydraulic cylinders 9 and 10 are arranged substantiallyparallel to the spindles 5 and 6, and are connected with the spindles 5and 6 via spline structures 26 and 27 respectively. A piston 11 isprovided to be slidable in the rotary hydraulic cylinder 9, and a piston12 is provided to be slidable in the rotary hydraulic cylinder 10. Thepistons 11 and 12 are provided with piston heads 11 a and 12 a at theirends respectively to be mated with sliding shoes 24 and 25 respectively.

The swash plates 7 and 8 comprise guiding and mating surfaces forguiding sliding shoes 24 and 25 respectively. The rotary hydrauliccylinders 9 and 10 are driven by the spindles 5 and 6 to rotate aboutcentral axes of the spindles respectively together with their pistons 11and 12 during the running of the hydraulic pump. Because the slidingshoes 24 and 25 remains always contact with the corresponding guidingand mating surfaces of the swash plates 7 and 8, the pistons 11 and 12can be slided axially and reciprocatingly in the rotary hydrauliccylinders 9 and 10. The rotary hydraulic cylinders 9 and 10 comprisetheir own separate outlets respectively, so that the moving pistons 11and 12 supply hydraulic oil for hydraulic operating components of theexcavator one independent of another.

Angles of inclination of the swash plates 7 and 8 relative to thespindles 5 and 6 are adjustable, so that reciprocating strokes of thepistons 11 and 12 in the rotary hydraulic cylinders 9 and 10 can beadjusted accordingly. For example, the swash plate 7 is shown, in theleft of FIG. 1, to be at a larger angle of inclination relative to anaxis perpendicular to the spindle 5 to set the maximum reciprocatingstroke of the piston 11 in the rotary hydraulic cylinder 9; and theswash plate 8 is shown, in the right of FIG. 1, to be at a smaller angleof inclination relative to an axis perpendicular to the spindle 6 to setthe minimum reciprocating stroke of the piston 12 in the rotaryhydraulic cylinder 10.

With reference to FIG. 2, a sliding bearing 14 is provided in thehousing 2 which is configured for providing sufficient support for thespindles 5 and 6. The sliding bearing can be configured as an integralor split bearing bush made of any suitable wear resistant metalmaterial, such as a bearing alloy or powder metallurgy material. Thesliding bearing 14 is disposed over the coupler 13 with an innercircumferential surface of the sliding bearing 14 in contact with anouter circumferential surface of the coupler 13.

The housing 2 comprises a supporting wall 2 a, and the supporting wall 2a is provided with a mounting hole for mounting the bearing 14 therein.

As shown in FIG. 2, preferably, the sliding bearing 14 is mounted in themounting hole via an adapting bushing 15 in order to protect thesupporting wall 2 a and improve service life of the sliding bearing 14.Preferably, the sliding bearing 14 and the adapting bushing 15 havesubstantially the same longitudinal length, and their longitudinallengths are greater than the thickness of the supporting wall 2 a in adirection of the central axes of the spindles 5 and 6.

As can be seen from FIG. 1, a majority of the spindle 5, the swash plate7 and the rotary hydraulic cylinder 9 are at the left side of thesupporting wall 2 a, while a majority of the spindle 6, the swash plate8 and the rotary hydraulic cylinder 10 are at the right side of thesupporting wall 2 a. Preferably, the two rotary hydraulic cylinders 9and 10 are disposed coaxially.

The adapting bushing 15 can be made of a metal material which is morewear resistant than the housing 2. For example, the adapting bushing 15is made of a steel material. Still for example, the adapting bushing 15can be made of a material same as or different from that of the slidingbearing 14. A circumferential flange 15 a extends out radially from anouter circumferential surface of the adapting bushing 15 near an end(for example, the left end in FIG. 2) of the adapting bushing 15 for thepurpose of positioning. The circumferential flange 15 a is configuredfor abutting against an end surface of the supporting wall 2 a so thatthe adapting bushing 15 can be fixed into position.

Upon mounting into position, an inner circumferential surface of theadapting bushing 15 is in contact with an outer circumferential surfaceof the sliding bearing 14, while the outer circumferential surface ofthe adapting bushing 15 is in contact with a surface of the mountinghole in the supporting wall 2 a. For a mechanical device working in badconditions, such as an excavator, a hydraulic pump according to theinvention incorporates the sliding bearing so that the structure becomessimpler and the enduring ability for heavy loads is improved. Theservice life of hydraulic pump is significantly prolonged and themanufacturing cost is reduced. In addition, according to the technicalsolutions of the invention, the sliding bearing 14 can be mounted in thehousing of hydraulic pump via the adapting bushing 15, and the wear tothe housing 2 itself is therefore reduced and the service life of thehydraulic pump is improved accordingly.

FIG. 3 and FIG. 4 show a hydraulic pump according to anotherillustrative embodiment of the invention. This hydraulic pump differsfrom the previous embodiment in that the coupler 13 comprises a pair ofsliding bearings 18 and 19 which are spaced from each other axially andmounted on the coupler 13. The sliding bearings 18 and 19 can be made ofthe same material as the sliding bearing 14 shown in FIG. 1.

Due to the sliding bearings 18 and 19 spaced axially, heat generatedduring the running of the hydraulic pump and in particular during therotating of the coupler 13 can be dissipated more rapidly, and thetemperature of the sliding bearings is reduced significantly. Thesliding bearings 18 and 19 have substantially the same axial length andare disposed over the coupler 13, so that inner circumferential surfacesof the sliding bearings 18 and 19 are in contact with the outercircumferential surface of the coupler 13. As can be seen from FIG. 4,the sliding bearings 18 and 19 are spaced from each other sysmetricallywith reference to a mid plane L of the coupler 13 which is perpendicularto the coupler 13.

Similar to the previous embodiment, the sliding bearings 18 and 19 areprovided with adapting bushings 16 and 17 respectively via which thesliding bearings 18 and 19 are mounted in the mounting hole in thesupporting wall 2 a of the housing 2. As shown in FIG. 4, the twoadapting bushings 16 and 17 may have same axial lengths as the slidingbearings 18 and 19 and extend over the sliding bearings 18 and 19. Uponmounting into position, inner circumferential surfaces of the adaptingbushings 16 and 17 are in contact with outer circumferential surfaces ofthe sliding bearings 18 and 19.

The adapting bushings 16 and 17 and the adapting bushings 15 may bemanufactured from the same material. Circumferential flanges 16 a and 17a extend out radially from outer circumferential surfaces of theadapting bushings 16 and 17 near ends of the adapting bushings 16 and 17approximate to the corresponding end surfaces of the supporting wall 2a, also for the purpose of the positioning. The circumferential flanges16 a and 17 a are configured for abutting against the corresponding endsurfaces of the supporting wall 2 a so that the adapting bushings 16 and17 can be fixed into position.

It can be found when comparing FIG. 2 with FIG. 4, for the couplers 13with the same axial length, through manufacturing the sliding bearing ofthe invention as two sliding bearings 18 and 19 axially spaced from eachother and/or manufacturing the adapting bushing of the invention as twosliding bushings 16 and 17 axially spaced from each other, the materialfrom which they are manufactured can be saved. This reduces themanufacturing cost accordingly because the material from which thesliding bearings and/or the adapting bushings are manufactured isexpensive.

As shown in FIG. 3, by way of the left swash plate 7 as an example, theswash plate 7 is stationary relative to the spindle 5 during the runningof the hydraulic pump, the rotary hydraulic cylinder 9 is driven by thespindle 5 to rotate about its central axis, and at the same time thepiston 11 moves reciprocatingly in the rotary hydraulic cylinder 9. Itcan be known from theoretically technical analysis known in the priorart, an action point O of a resultant force the rotary hydrauliccylinder 9 applies upon the spindle 5 is situated on the central axis ofthe spindle 5.

The sliding bearing 18 has a center of gravity G, and the axial lengthfrom the center of gravity G to the action point O of the resultantforce is A. A bending moment will be generated at the area in which thebearing is contacted with the mounting hole during the running of thehydraulic pump. Excessive bending moment may cause the spindle tovibrate or even destabilize, and so affect the work efficiency of thehydraulic pump. It can known from the theoretical calculation that theamount of the bending moment depends on the distance between the centerof gravity of the sliding bearing and the action point O of theresultant force. The smaller the distance is, the smaller the bendingmoment generated during the running of the hydraulic pump is, and thenthe smaller the vibration is.

FIG. 3 shows a center of gravity G′ of the coupler 13. For the slidingbearing 14 shown in FIG. 1, the center of gravity of the sliding bearing14 is consistent with the center of gravity G′ of the coupler 13. Thatis to say, the distance between the center of gravity of the slidingbearing 14 shown in FIG. 1 and the action point O of the resultant forceis A′. It can be clearly seen from FIG. 3 that the distance A is smallerthan the distance A′ because the sliding bearings 18 and 19 are disposedover the coupler 13 with one spaced from each another. Consequently,compared with the embodiment shown in FIG. 1, the hydraulic pumpaccording to the embodiment shown in FIG. 3 has a smaller bending momentgenerated at the bearing during running, and thus the vibrationgenerated on the spindle is smaller or even eliminated. The workefficiency of the hydraulic pump is improved.

The same also applies to the right swash plate 8, the spindle 6, therotary hydraulic cylinder 10 and the piston 12 shown in FIG. 3.

FIG. 5 shows a hydraulic pump according to a further embodiment of theinvention. The supporting wall 2 a is formed with a through hole 20therein which extends in a direction perpendicular to the central axesof the spindles 5 and 6. The through hole 20 is aligned with andcommunicated with a gap between the sliding bearings 18 and 19 so thatlubricant oil can be injected into the gap to lubricate the bearings andat the same time to lower the temperature of the sliding bearings 18 and19 when the spindles 5 and 6 rotate. It is conceivable that the throughhole 20 can be further configured for receiving the oil leaked from therotary hydraulic cylinders 9 and 10 during their running. In this way,the received oil can pass by the sliding bearings 18 and 19, cause thetemperature of the bearings to be lowered, and then flows out of thethrough hole.

In another embodiment, a pair of spherical splines are mounted betweenthe coupler 13 and the spindles 5, 6.

Optionally, in order to further improve lubricating and temperaturedecreasing effect, a plurality of through holes 20 can be provided inthe supporting wall 2 a, which extend perpendicularly to the centralaxes of the spindles 5 and 6, and all the through holes 20 are alignedand communicated with the gap between the sliding bearings 18 and 19. Inaddition, optionally, the through hole 20 may be arranged at anotherangle with reference to the central axes of the spindles 5 and 6.

To facilitate assembling, as shown in FIGS. 2, 4 and 5, the slidingbearings 14, 18 and 19 are manufactured preferably with chamfers atouter surfaces of opposite ends respectively, so that the slidingbearings can be inserted into the adapting bushings 15 and 17 smoothlywhen assembling, and the lubricant oil can enter the areas between thesliding bearings and the mating components around more easily.

Although in the above embodiments the sliding bearing 14 or the slidingbearings 18 and 19 according to the invention is/are shown to supportthe coupler 13 between the two spindles 5 and 6, it is conceivable that,in a case that the swash plates 7 and 8 in the hydraulic pump are onlydriven by a single spindle, the sliding bearing 14 or the slidingbearings 18 and 19 according to the invention may be supported in themounting hole of the supporting wall 2 a at a substantially centrallocation of the single the spindle in its longitudinal direction via theadapting bushing 15 or the adapting bushings 16 and 17.

It is conceivable that, in the embodiment shown in FIG. 4, the adaptingbushings 16 and 17 can be replaced with the adapting bushing 15; or thesliding bearings 18 and 19 can be replaced with the sliding bearing 14.It is conceivable that, in the embodiment shown in FIG. 5, the slidingbearings 18 and 19 can be replaced with the sliding bearing 14. Inaddition, it is conceivable that the axial separation between theadapting bushings 16 and 17 may also be different from the axialseparation between the sliding bearings 18 and 19.

Although the sliding bearing 14 or the sliding bearings 18 and 19 is/areconfigured for supporting the coupler 13 in the supporting wall 2 ainside the housing 2 in the embodiments of the invention, it isconceivable that the sliding bearing 14 or the sliding bearings 18 and19 may also be configured as bearings in the end cap 3 and/or the endcap 4 for supporting the spindle 5 and/or the spindle 6.

It is conceivable that, in a case that N (in which N is an integerlarger than 2) spindles are provided coaxially in a hydraulic pump andare connected via N−1 couplers, the sliding bearing 14 or the slidingbearings 18 and 19 may be provided at locations of the N−1 couplersrespectively for supporting the respective spindles.

According to the invention, a sliding bearing with a relative simplestructure is incorporated into a hydraulic pump, which results in animproved stress distribution, a prolonged service life of the hydraulicpump, and at the same time reduced manufacturing and assembly cost. Inaddition, through providing the sliding bearings spaced from each otheraxially, heat generated during the running of a spindle can bedissipated efficiently, the working temperature of the bearing can bereduced, and thus the failure risk is avoided. Through providing an oilguiding hole in a housing of the hydraulic pump which is aligned andcommunicated with a gap between the sliding bearings, the bearing can belubricated efficiently and the heat generated during the rotation can betaken away efficiently. This may further reduce the working temperatureof the bearing.

Although special embodiments of the invention have been described above,they are presented only for illustration purpose and not intended tolimit the scope of the invention. Rather, various substitutions,variants and changes can be conceived without departing from the spiritand scope of the invention.

1. A hydraulic pump for an excavator comprising: a housing having asupporting wall extending therein; a pair of rotary hydraulic cylindersprovided in the housing, each of the rotary hydraulic cylinders beingprovided with a respective piston which is movable reciprocatingly inthe rotary hydraulic cylinder; and a pair of spindles disposed parallelto the rotary hydraulic cylinders, the spindles being connected witheach other via a coupler and driving the rotary hydraulic cylinders torotate about respective central axes, each of the rotary hydrauliccylinders comprising a swash plate for receiving and guiding therespective piston, and the swash plate being stationary relative to therespective spindle, wherein the supporting wall comprises a mountinghole, and the coupler is supported in the mounting hole by means of asliding bearing.
 2. The hydraulic pump according to claim 1, furthercomprising an adapting bushing, wherein the sliding bearing is mountedin the mounting hole via the adapting bushing so that the adaptingbushing is located between an outer circumferential surface of thesliding bearing and an inner surface of the mounting hole.
 3. Thehydraulic pump according to claim 2, wherein a circumferential flangeextends out radially from an outer circumferential surface of theadapting bushing near an end of the adapting bushing which is adjacentto a surface of the supporting wall, and the circumferential flange isconfigured for contacting with the supporting wall.
 4. The hydraulicpump according to claim 3, wherein the sliding bearing is configured asa pair of sliding bearings axially spaced from each other.
 5. Thehydraulic pump according to claim 4, wherein the adapting bushing isconfigured as a pair of adapting bushings axially spaced from eachother.
 6. The hydraulic pump according to claim 5, wherein thesupporting wall is formed with an oil guiding hole, and the oil guidinghole is aligned with and communicated with an axial gap between theadapting bushings.
 7. The hydraulic pump according to claim 6, whereinthe oil guiding hole is configured for receiving oil leaked in runningof the rotary hydraulic cylinders, so that the leaked oil can pass bythe sliding bearing and flow out via the oil guiding hole after coolingthe bearings.
 8. The hydraulic pump according to claim 2, wherein atleast one of the sliding bearing and the adapting bushing is providedwith chamfers at opposite ends.
 9. The hydraulic pump according to claim2, wherein the adapting bushing is made of an alloy steel material, andthe sliding bearing is made of a powder metallurgy material.
 10. Thehydraulic pump according to claim 1, wherein a pair of spherical splinesare mounted between the coupler and the spindles.
 11. The hydraulic pumpaccording to claim 7, wherein at least one of the sliding bearing andthe adapting bushing is provided with chamfers at opposite ends.
 12. Thehydraulic pump according to any claim 11, wherein the adapting bushingis made of an alloy steel material, and the sliding bearing is made of apowder metallurgy material.
 13. The hydraulic pump according to claim12, wherein a pair of spherical splines are mounted between the couplerand the spindles.
 14. An excavator comprising a hydraulic pump accordingto claim 1.